Avalanche photodiode (APD) semi-conductor technology recently developed at RMD has demonstrated great promise in the form of compact arrays of detectors. While, APD arrays are capable of providing the basis for a new generation of high-resolution, photon-imaging systems, we have seen it is not possible to use conventional pulse-processing circuitry to support the many signals generated by these arrays. Due to the high detector density, compact size, and unique electronic features of APD arrays, conventional electronics quickly become problematic to the implementation to APD arrays in imaging systems. Thus, there is an immediate need for the development of a application-specific, integrated- circuit (ASIC) preamplifier and shaping circuit that is compact, has many channels, has high performance, and is suitable for APD arrays. As the focus of the work proposed here, we will undertake the research necessary to develop an ASIC for implementation with APD arrays. Additional research will be carried out to combine the ASIC with RMD APD arrays to create a PET detector module. We expect that replacing photomultiplier tubes and their electronics with APD arrays and ASIC circuitry, small animal PET technology can be advanced to areas of new high-resolution research at lower cost with a direct benefit to humans. PROPOSED COMMERCIAL APPLICATIONS: Medical applications using small volume PET systems such as; breast and small animal imaging. Additional medical applications include whole body PET scanners, gamma cameras, and probes. Complementary applications include nuclear physics, astronomy, and biological and chemical assay systems.